import java.io.IOException; 
  
import org.apache.hadoop.conf.Configuration; 
import org.apache.hadoop.fs.FSDataInputStream; 
import org.apache.hadoop.fs.FileSystem; 
import org.apache.hadoop.fs.Path; 
import org.apache.hadoop.io.LongWritable; 
import org.apache.hadoop.io.Text; 
import org.apache.hadoop.io.compress.CompressionCodec; 
import org.apache.hadoop.io.compress.CompressionCodecFactory; 
import org.apache.hadoop.mapreduce.InputSplit; 
import org.apache.hadoop.mapreduce.RecordReader; 
import org.apache.hadoop.mapreduce.TaskAttemptContext; 
import org.apache.hadoop.mapreduce.lib.input.FileSplit; 
import org.apache.hadoop.util.LineReader; 
  
public class KeyValueTextRecordReader extends RecordReader<Text, Text> { 
    //private static final Logger logger = Logger.getLogger((LineRecordReader.class.getCanonicalName())); 
  
    @Override 
    public void initialize(InputSplit genericSplit, TaskAttemptContext context) throws IOException { 
        FileSplit split = (FileSplit) genericSplit; 
        Configuration job = context.getConfiguration(); 
        this.maxLineLength = job.getInt("mapred.linerecordreader.maxlength", 
        Integer.MAX_VALUE); 
        start = split.getStart(); 
        end = start + split.getLength(); 
        final Path file = split.getPath(); 
        compressionCodecs = new CompressionCodecFactory(job); 
        final CompressionCodec codec = compressionCodecs.getCodec(file); 
          
        // open the file and seek to the start of the split 
        FileSystem fs = file.getFileSystem(job); 
        FSDataInputStream fileIn = fs.open(split.getPath()); 
        boolean skipFirstLine = false; 
        if (codec != null) { 
            in = new LineReader(codec.createInputStream(fileIn), job); 
            end = Long.MAX_VALUE; 
        } else { 
            if (start != 0) { 
                skipFirstLine = true; 
                --start; 
                fileIn.seek(start); 
            } 
            in = new LineReader(fileIn, job); 
        } 
        if (skipFirstLine) { // skip first line and re-establish "start". 
            start += in.readLine(new Text(), 0, 
                    (int) Math.min((long) Integer.MAX_VALUE, end - start)); 
        } 
        this.pos = start; 
    } 
  
    @Override      
    public boolean nextKeyValue() throws IOException { 
        if (key == null) { 
            key = new LongWritable(); 
        } 
        key.set(pos); 
        if (value == null) { 
            value = new Text(); 
        } 
        int newSize = 0; 
        while (pos < end) { 
            newSize = in.readLine(value, maxLineLength, 
                    Math.max((int) Math.min(Integer.MAX_VALUE, end - pos), 
                            maxLineLength)); 
            if (newSize == 0) { 
                break; 
            } 
            pos += newSize; 
            if (newSize < maxLineLength) { 
                break; 
            }      
            // line too long. try again 
            //logger.info("Skipped line of size " + newSize + " at pos " + (pos - newSize)); 
        } 
        if (newSize == 0) { 
            key = null; 
            value = null; 
            return false; 
        } else { 
            return true; 
        } 
    } 
      
    @Override 
    public Text getCurrentKey() { 
        try{ 
            tempValue = value.toString(); 
            return new Text(tempValue.substring(0, tempValue.indexOf("\t")    )); 
        }catch(Exception ex){ 
            return value; 
        } 
    } 
      
    @Override 
    public Text getCurrentValue() { 
        try{ 
            return new Text(value.toString().split("\t")[1]); 
        }catch(Exception ex){ 
            return nullText; 
        } 
    } 
      
    /** 
    * Get the progress within the split 
    */ 
    @Override 
    public float getProgress() { 
        if (start == end) { 
            return 0.0f; 
        } else { 
            return Math.min(1.0f, (pos - start) / (float) (end - start)); 
        } 
    } 
      
    @Override 
    public synchronized void close() throws IOException { 
        if (in != null) { 
            in.close(); 
        } 
    } 
      
    private CompressionCodecFactory compressionCodecs = null; 
    private long start; 
    private long pos; 
    private String tempValue; 
    private long end; 
    private LineReader in; 
    private int maxLineLength; 
    private LongWritable key = null; 
    private Text value = null; 
    private final Text nullText = new Text(""); 
  
}
